Width of Pinhole Camera Aperture for 12cm Spot Light

[G01]

A point source of light 2.0m away from the a pinhole camera creats a 12cm wide spot of light on the screen 1.0 deep inside the camera. How wide is the aperture of the camera.

I thought this was a magnification problem, so I set up the equation:

h_i = .12m, h_o = x, s_i = 1m, s_o = 2.0m

\frac{h_i}{h_o} = \frac{s_i}{s_o}

\frac{.12m}{x} = \frac{1m}{2m}

.24m = x The answer is .08m. I'm getting many of these optics problems wrong and I don't know why. I need some help and several of the problems I have posted have gone without answers. I hope someone answers this one. Thank you for your help.

 

[Tide]

The numerator on the right side should be 3 meters. You're trying to set up a proportion but you're not equating the correct ratios.

 

[G01]

Yes, I just realized this, that should be 3/2 not 1/2. Screwed up my similar triangles... Thank you so much..